Geometrical instrument



June 4, 1946. SCHWEND 2,401,321

GEOMETRICAL INSTRUMENT Filed May 17,

Patented June 4, 1946 UNITED STATES PATENT OFFICE Fred N. Schwend, Los Angeles, Calif.

Application May 1'7, 1944, Serial No. 535.960

Claims. 1

This invention relates to geometrical instruments and particularly to quick-motion adjustments for compasses, dividers, etc., in which the legs thereof are adjusted by a manipulable screw.

Heretofore, various quick-motion adjustments have been provided for dividers, etc., most of which comprise a split-nut device threaded on a screw which passes through one leg of the instrument and is suitably attached to the other. Rotation of the split-nut bears against the adjacent leg to adjust the same relative to the other leg. Such devices are not adaptable to the type of instrument now in extensive use in which a screw having oppositely threaded sections is threaded through both legs of the instrument. In this type considerable time and wear are incurred in adjusting the instrument to different spacing of its legs, particularly when such spacing varies a large amount. I

One object of the present invention is to automatically compensate for wear in the threaded connections of an instrument of the latter mentioned type.

Another object is to reduce the amount of time required to adjust the legs of an instrument of the above type. A further object is to reduce the wear of the threaded connection.

A further object is to reduce the amount of clearance or back-lash in the threaded connection.

Fig. 1 is a front view of one form of my invention.

Fig. 2 is a sectional view taken along the line 2-2 of Fig. 1 illustrating the quick-motion adjustment.

Fig. 3 is a transverse sectional view taken along the line 3-3 of Fig. 2.

Fig. 4 is a sectional plan view taken along the line 44 of Fig. 2.

Fig. 5 is a sectional plan view taken along the lines 5-5 of Fig. 6 illustrating a modified form of the invention.

Fig. 6 is a side-elevational view, partly in section, and is taken along the line 56 of Fig. 5.

Fig. '7 is a modified form of the construction illustrated in Figs. 1 to 4.

Referring particularly to Figs. 1 to 4, inclusive, the instrument chosen for the purpose of illustrating the present invention is a bow-compass having legs ll terminating in a pivot i2 and a lead l3. The upper end of each leg is formed with an arcuate surface l5 fitted over a pivot pin l6 and held in place against the pin by a circular spring I! pressing inwardly against both legs.

An adjusting screw I8 is provided for varying the spacing of the legs. This screw comprises section 20 and 2| having oppositely disposed threads, between which is located a serrated disk integral with the screw. The screw passes through transverse openings 23 in the legs I I.

In accordance with the present invention, the threaded connection for each leg of the instrument comprises a pivotal split-nut device consisting of a pair of bearing elements or pins 22 rockably and slidably fitted in co-axial bearings formed in the respective leg. The adjacent ends of the pins are threaded to normally form the threaded connection for the screw.

Each pin has a groove 24 formed therein and embraced by bent-over ears 25 (Fig. 4) formed in levers 26 and 21, both of which are pivoted intermediate their ends on a transversely extended bearing pin 28 passing through the respective leg.

A leaf spring 30 (Fig. 2 is fixed in any suitable manner to each lever and bears against the respective leg, thus tending to hold the pins 22 against the screw. In view of the spring force exerted against the pins, they will always normally fit snugly against the screw and will take up any wear occurring in the threaded connections as well as prevent any clearance or backlash in the connections.

A rod 32, terminating in a knob 33, is passed through an opening in spring I1 and through the pivot pin l6, being suitably fixed in the latter. The lower end of rod 32 extends into groove 33 in the disk 22'.

When it is desired to adjust the legs of the compass over a considerable distance the two pairs of levers 26 and 21 are pressed inward, removing the pins 22 from engagement with the screw so that the legs may be quickly adjusted to the desired spacing. During this adjustment the rod 32 will prevent longitudinal movement of the screw relative to the bearing pin "5 so that it will always remain centered relative to the legs.

Figs. 5 and 6 illustrate a modified form of the invention in which bearing elements or pins 22a are slidably and rockably mounted in the legs of the instrument. The pins have their inner ends elongated to providea long thread surface for engagement with the threads of the adjusting screw. A pair of U-shaped springs 35 embrace the ends of the elongated sections of the pins 22a to normally press the same against the screw. Lugs 35 and 36' are formed on the lower ends of the elongations of the pins, and on these are mounted pivot pins 31 and 38 connected to the end and intermediate portions, respectively, of a manipulable lever 40. The latter has a thumb piece 4| which may be pressed inward toward the screw to spread the pins apart so as to disengage the same from the screw and thus permit quick adjustment of the legs of the instrument to a desired spacing.

Fig. 7 illustrates a modified form of the construction illustrated in Figs. 1 to 4, inclusive, in which the levers 26a and 2111 are pivoted on pins 28a and are connected to pins 22 in a manner similar to that shown in Figs. 2 and 3. In this case the free ends of the levers extend upwardly over the pivot pin l6, terminating in overlapping buttons 43 which may be pressed inwardly, thus simultaneously releasing the threaded connections of both legs.

Having thus described the invention what I claim as new and desire to secure by Letters Patent is:

1. A geometrical instrument comprising adjustably spaced legs, a screw member for adjustin-g said legs, threaded connections between said screw member and said legs, at least one of said connections comprising a pair of coaxially aligned pins slidably and rotatably mounted in one of said legs, the adjacent ends of said pins being threaded to threadably engage said screw member, yieldablemeans for pressing said pin into engagement with said screw'member, and manipulable levers pivoted on said leg and operatively connected to said pins for removing said pins from engagement with said screw member.

2. A geometrical instrument comprising adjustably spaced legs, a screw member for adjusting said legs, threaded connections between said screw member andsaid legs, at least one of said connections comprising a pair of coaxially aligned elements slidably mounted in one of said legs for movement toward and away from each other, the adjacent ends of said elements being threaded to threadably engage said screw member, spring means for pressing said elements into engagement with said screw member, and a manipulable lever pivotally connected to said elements for moving the same away from each other.

3. A geometrical instrument comprising adjustably spaced legs, a screw member for adjusting said legs, threaded connections between said screw member and said legs, at least one of said connections comprising a pair of co-axially aligned elements rotatably and slidably mounted in one of said legs for movement toward and away from each other, the adjacent ends of said elements being threaded to threadably engage said screw member, spring means for pressing said elements into engagement with said screw member, and a manipulable lever pivotally connected to said elements for moving the same toward and away from each other.

4. A geometrical instrument comprising a pivot, legs connected to said pivot and adjustable thereabout, a screw member for adjusting said legs, threaded connections between said screw member and said legs, said connections comprising a pair of elements rotatably and slidably mounted in each of said legs for movement toward and away from each other, the adjacent ends of each pair of said elements being threaded to threadably engage said screw member, means for pressing said elements against said screw member, means for removing said elements from engagement with said screw member whereby to permit adjustment of said legs relative to said screw member, and means for preventing longitudinal movement of said screw member relative to said pivot.

5. A geometrical instrument comprising a pivot, legs connected to said pivot and adjustable thereabout, a screw member for adjusting said legs, threaded connections between said screw member and said legs, said connections comprising a pair of elements slidably mounted in each of said legs for movement toward and away from each other, the adjacent ends of each pair of said elements being threaded to threadably engage said screw member, means for pressing said elements against said screw member, and means for removing said elements from engagement with said screw member comprising levers for said elements pivotally mounted on said legs, the free ends of certain of said levers overlapping the free ends of adjacent ones of said levers adjacent said pivot.

. FRED N. SCHWEND. 

